NIWA issued a response statement regarding the charges leveled by The NZ Climate Science Coalition here:
http://www.niwa.co.nz/our-science/climate/news/all/niwa-confirms-temperature-rise
They say:
Warming over New Zealand through the past century is unequivocal.
NIWA’s analysis of measured temperatures uses internationally accepted techniques, including making adjustments for changes such as movement of measurement sites. For example, in Wellington, early temperature measurements were made near sea level, but in 1928 the measurement site was moved from Thorndon (3 metres above sea level) to Kelburn (125 m above sea level). The Kelburn site is on average 0.8°C cooler than Thorndon, because of the extra height above sea level.
I’m not too impressed, especially when you see where the weather station for National Institute of Water and Atmosphere (NIWA) is, right on the rooftop next to the air conditioners:
Here is the station survey: NIWA_station_survey (PDF) and the Google Earth KML file
Thanks to: Dieuwe de Boer who did a good portion of station surveys in New Zealand last year.
The NZ Climate Science Coalition responds:
NIWA’s explanation raises major new questions
The NIWA climate controversy took a new twist tonight with the release of new data from the government run climate agency.
Reeling from claims that it has massaged data to show a 150 year warming trend where there isn’t one, NIWA’s chief climate scientist David Wratt, an IPCC vice-chair on the 2007 AR4 report, issued a news release stating adjustments had been made to compensate for changes in sensor locations over the years.
While such an adjustment is valid, it needs to be fully explained so other scientists can test the reasonableness of the adjustment.
Wratt is refusing to release data his organisation claims to have justifying adjustments on other weather stations, meaning the science cannot be reviewed. However, he has released information relating to Wellington temperature readings, and they make for interesting reading.
Here’s the rub. Up until 1927, temperatures for Wellington had been taken at Thorndon, only 3 m above sea level and an inner-city suburb. That station closed and, as I suspected in my earlier post, there is no overlap data allowing a comparison between Thorndon and Kelburn, where the gauge moved, at an altitude of 135 metres.
With no overlap of continuous temperature readings from both sites, there is no way to truly know how temperatures should be properly adjusted to compensate for the location shift.
Wratt told Investigate earlier there was international agreement on how to make temperature adjustments, and in the news release tonight he elaborates on that:
“Thus, if one measurement station is closed (or data missing for a period), it is acceptable to replace it with another nearby site provided an adjustment is made to the average temperature difference between the sites.”
Except, except, it all hinges on the quality of the reasoning that goes into making that adjustment. If it were me, I would have slung up a temperature station in the disused location again and worked out over a year the average offset between Thorndon and Kelburn. It’s not perfect, after all we are talking about a switch in 1928, but it would be something. But NIWA didn’t do that.
Instead, as their news release records, they simply guessed that the readings taken at Wellington Airport would be similar to Thorndon, simply because both sites are only a few metres above sea level.
Airport records temps about 0.79C above Kelburn on average, so NIWA simply said to themselves, “that’ll do” and made the Airport/Kelburn offset the official offset for Thorndon/Kelburn as well, even though no comparison study of the latter scenario has ever been done.
Here’s the raw data, from NIWA tonight, illustrating temp readings at their three Wellington locations since 1900:
What’s interesting is that if you leave Kelburn out of the equation, Thorndon in 1910 is not far below Airport 2010. Perhaps that gave NIWA some confidence that the two locations were equivalent, but I’m betting Thorndon a hundred years ago was very different from an international airport now.
Nonetheless, NIWA took its one-size-fits all “adjustment and altered Thordon and the Airport to match Kelburn for the sake of the data on their website and for official climate purposes.
In their own words, NIWA describe their logic thus.
- Where there is an overlap in time between two records (such as Wellington Airport and Kelburn), it is a simple matter to calculate the average offset and adjust one site relative to the other.
- Wellington Airport is +0.79°C warmer than Kelburn, which matches well with measurements in many parts of the world for how rapidly temperature decreases with altitude.
- Thorndon (closed 31 Dec 1927) has no overlap with Kelburn (opened 1 Jan 1928). For the purpose of illustration, we have applied the same offset to Thorndon as was calculated for the Airport.
- The final “adjusted” temperature curve is used to draw inferences about Wellington temperature change over the 20th century. The records must be adjusted for the change to a different Wellington location
Now, it may be that there was a good and obvious reason to adjust Wellington temps. My question remains, however: is applying a temperature example from 15km away in a different climate zone a valid way of rearranging historical data?
And my other question to David Wratt also remains: we’d all like to see the metholdology and reasoning behind adjustments on all the other sites as well.
I sort-of agree that you don’t need to stitch them together, but there is a problem there. Since the data is noisy, a trend over a short period doesn’t tell you much. So if you take all these pieces, take a trend on each, and average, I’m not sure how good that would be. After all, the alleged AGW trend is very small compared to the intra-annual variation, so only long term averages bring it out of the noise.
I’d have to look at the math a bit on that.
I’d be interested when you done so digging around.
I’ve done some and from what I can tell it does work.
The actual pieces are going to be relatively long, several years in most cases.
I’m sure statisticians have looked at this in depth. It should be possible to read up on methods for that. Time series analysis is a very big deal in lots of fields.
I’m probably not going to have time to do much more fiddling. It would be interesting if some of the statisticians who read this blog, or some of the posters, would comment on how one would calculate trends without doing this seemingly unnecessary local trend generation.
It occurred to me that two stations do run concurrently for a long period of time, and that there may be some information that could be gathered from a comparison of the two.
Kelburn data is available from 1962 through 2008 (complemented by Kelburn AWS for the last four years), and Wellington Aero (Airport) data exists from 1962 through 2008.
The average temperature difference between these locations from 1962 through 2008 is 0.6C. NIWA adjusted Thorndon the same amount as the “Airport” location, by .8C.
There is no trend in the stations differences between 1962 and 2008, although recently, from 1995 through 2008 the difference has been .9C. As an aside, from 1995 through 2008, Kelburn has a .2C decreasing linear trend, while Aero has a .2C increasing trend. Both trend downwards from 2000 through 2008.
Analyzing a comparison chart of the two station records, the long term average can be clearly seen to be affected the most by times of steep increases or decreases in temperature, which brings the stations temps closer together and affects the long term average differential.
A graph of the Thorndon temps is a good example of steep increases and decreases. If differences between stations are an indication of lapse rate, using the best estimate of a real, long term local average lapse rate would necessitate adjusting Thorndon down by .6C, not .8C.
It is entirely possible and IMO likely that the Wellington area has not experienced an overall increasing trend of more than a couple tenths of a degree in a century. Time of measurement errors likely prevail throughout earlier records, and as more attention was paid to climate change in the mid 70s, more effort and more records were likely done and kept which could easily cause an increasing divergence between the old and newer records. Local land use changes could have an effect, and could station UHI, for example with the two airport stations that combine in the NIWA record, the station that NIWA combines with “AERO” being an average of .2C higher than the other operating station which is not used by NIWA in their graph.
If all this is taken into consideration along with an assumption that Kelburn itself after 2000 read a couple tenths of a degree higher due to siting or UHI problems, Wellington trend is flat between 1913 – 2009.
John Moore (19:32:05) :
“I’m probably not going to have time to do much more fiddling.”
Yes you do. Come on, don’t quit now.
“One thing to do would be to put stations in historical locations (like Thorndon) no longer present and record a few years of calibration data. That would help anywhere you didn’t have enough overlap.”
Time travel hasn’t been developed to the degree necessary. (Sorry, couldn’t resist)
That would not provide you with overlap. Lapse rates change with the weather. You’d be calibrating Thorndon with 2008 weather.
“Another would be to try to measure average lapse rate for similar station differences in the same general area, and crank that in.”
Yes, but we don’t have the average lapse rate for Thorndon, nor any stations that overlap.
“nother would be to try to create a meteorological model of each station, and use it to “forecast” the past in some sense.”
Perhaps, but the old records are scarce enough, there is not much reason to expect that in the late 1800s and early 1900s detailed enough records would have been kept on daily basis of such variables you mention. And even now models have a hard time forecasting precise temperatures to tenths of a degree. It’s one reason we use thermometers.
“NIWA obviously didn’t try very many of these. If I were them, I’d use the adverse publicity to get funding to do more of this sort of thing, while at the same time making everything transparent.”
That isn’t obvious. The guy who started this survey has published work. NIWA claims to have a pamphlet in their library of the methodology used as well. I’ve read a little, about studying old sea charts and wind patterns, pictures, tea leaves and such.
But when it comes right down to it, a massive amount of data and analysis could have been attempted; how much was actually considered is a different matter, and whether there is information anywhere that could support a serious scientific study may be elusive or nonexistent. It could have been not much more than “ok, do the lapse rate, no stinkin uhi, I got to hurry off, busy with a bunch of different things, thats enough to get through review, here ya go” kind of thing. I have very little confidence that isn’t closer to the truth.
RE: your 20:00:54 comment… Not sure what you mean. What data did u use? Annual averages or monthly? I tried it with annual and did see a bit of a trend.
………
“That would not provide you with overlap. Lapse rates change with the weather.
You’d be calibrating Thorndon with 2008 weather. ”
Better than nothing, not as good as having had the overlap in the first place.
On the met models, I didn’t mean the GCM’s used in modern forecasting. I meant simple stuff to take into account local conditions, based on climatological data like wind patters, cloud patterns, etc.
I suspect your surmise at the end of the previous comment is closest to the truth.
I
John Moore (22:45:46) :
“RE: your 20:00:54 comment… Not sure what you mean. What data did u use? Annual averages or monthly? I tried it with annual and did see a bit of a trend.”
I used annual from monthly averages. What trend do you mean? For the ’62 to ’08 stations difference? If so, I wouldn’t expect a trend, but a pattern indicating weather shifts. Oh, I made a mistake, it looks like the difference is greater, not less, when there are dramatic ups and downs in temperature. Don’t have a clue as to what could be the reason behind that.
“That would not provide you with overlap. Lapse rates change with the weather.
You’d be calibrating Thorndon with 2008 weather. ”
Better than nothing, not as good as having had the overlap in the first place.”
Nothing is not better than nothing. Might as well read tea leaves. You can do that now, though, just as I did with the airport and Kelburn, and lower Thorndon by .9C, or use the Karori station and adjust Thorndon by 75.1C. At least a long term record of two stations like I did is something, as weather comes and goes but a long average has a better chance of hitting on a more accurate average.
“On the met models, I didn’t mean the GCM’s used in modern forecasting. I meant simple stuff to take into account local conditions, based on climatological data like wind patters, cloud patterns, etc.”
It’s far from being simple, and it changes. I wouldn’t want to be the one that spent years developing algorithms and programs just to find out after firing it up that it didn’t predict temperatures within a degree in a week.
I suspect your surmise at the end of the previous comment is closest to the truth.
The adjustment of exactly the standard lapse rate makes me the most suspicious.
John Moore (22:45:46) :
“RE: your 20:00:54 comment… Not sure what you mean. What data did u use? Annual averages or monthly? I tried it with annual and did see a bit of a trend.”
If you meant the part about a trend being no more than 0.2C or flat,
The first 14 years (Thorndon) adjusted down 0.6C averages 12.6C.
The last 14 years (Kelburn) adjusted down 0.2C averages 12.8C.
So there is an average increase from those periods of 0.2C.
The linear trends for Thorndon first 14 years and Kelburn last 14 years are both descending. This, if you trust “trends”, indicates that Thorndon was cooling and Kelburn is cooling, which puts any real increasing trend in doubt, which is why I said Wellington is flat.
Linear trends can be deceptive, and can be more so for a long period than a short. If all data is combined and plotted from 1913 to 2008, a linear trend = 0.6C.
But a little test shows the problem with linear trends such as this.
Take a 20 year sample of temps shown below, the linear trend increases 0.2C, even though temps end up cooler than the beginning:
year temp
2000 12
2001 12
2002 12
2003 12
2004 12
2005 8
2006 8
2007 8
2008 9
2009 9
2010 10
2011 10
2012 11
2013 11
2014 12
2015 12
2016 11
2017 11
2018 11
2019 11
2020 11
In the temperature series above ( Glenn (14:07:12)) we don’t know what the temp before the beginning year was. The temperature lowered, then rose and held to just under the value of the first years. A linear trend of this series shows an increase of about 0.2 degrees.
If the series is extended a hundred years to 2020, all with 11 degrees, the linear trend STILL increases by 0.2 degrees.
Proof of global warming for hundreds of years.
That’s because extrapolation is a very bad idea.
Posted on “Beach blanket brrr-go”
“Mr Lynn (16:54:38) :
Now a paper from 1980 throws all the New Zealand data out:”
http://www.investigatemagazine.com/australia/latestissue.pdf
Includes scanned copy of a 1980s journal article.
http://www.investigatemagazine.com/hessell1980.pdf
Wow, Salinger, Trenberth, Lawrence, these guys go way back.
Anthony, if you need anything in Northern IL, Southern WI, let me know.